WASHINGTON, D.C. - Claims by a NASA scientist last week to have discovered a microbe that substitutes arsenic for phosphorus in its DNA have encountered pushback from at least one scientist.

Last week, NASA held a widely covered press conference at which a team led by microbiologist Dr. Felisia Wolfs-Simon had found a microbe in Mono Lake, Calif., capable of replacing phosphorus - one of the key building blocks of life on Earth - with arsenic.

NASA planetary scientists hailed the findings, published in the journal Nature, as opening the door to new possibilities for life in the universe.

Outside experts are hoping for some clarity at another event today. Employees and the public are invited to a scientific presentation by U.S. Geological Survey research hydrologist Dr. Ronald Oremland about the Mono Lake research.